Telephone trunking system.



' G. S. WINSTON. TELEPHONE TRUNKING SYSTEM. APPLICATION FILED JAN. 3. 1905.

Patented Feb. 2,-1909. w- 5H!"- P BL To all whom it may concern:

pursue the reruns lorr es,

CHARLES S. WINSTON, OF CHICAGO ILLINOIS, ASSIGNOR TO KELLOGG SWITOHBOABD &

SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TIEInFJPHOlTE TRUNK-ING- SYSTEM.

Specification of Letters Patent.

Patented Feb. 52, 1909;.

Application filed January 3, 1905. Serial No. 239,370.

Be it known that LCHAnLss S. Wrnsrou, a citizen oft-he United States, residing at Chicago, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Telephone Trunking Systoms, of which the following is a specification.

My invention relates to improvements in telephone trunk circuits, and particularly in such circuits intended for use between magneto and common battery ofiices.

One object of the invention is to provide simple means for positively throwing the drop or other, signal in the magneto cord circuit when the common battery subscriber returns his receiver to the hook.

Other objects are to provide simple and inexpensive apparatus for suitably carrying out the various operations involved in establishing and supervising connections between central'ofiices.

To the accomplishmen'tof these and such other objects as may hereinafter appear, I provide the apparatus hereinafter more -i'ullydescribcd and illustrated in the accompanying drawing in which the figure isa diagram of a trunk circuit extending be tween a magneto and a common battery telephone oflice.

At the oflice the usual magneto cord circuit is shown and is providcd'with a calling plug 1?, a drop D bridged thereacross, and a suitable ringing generator 2. The operators telephone set and the answering plug of this circuit are not shown but will,

be understood as connected in the ordinary way. Thetrunk circuit at this oiiiceis provided with a springjack J by means of which the'cord circuit may be connected with the trunk. -At the ofiice C the trunk is provided with the plug P adapted to connect with the springj ack J of'thetelephone line L which 1s of ,the so-called two-wire type. A repeating coil W conductively divides but inductively unites the outgoing end of the trunk with the incoming end,

When a call received at the magneto oiiice for connection witha line terminating at the common battery office, the cailing plug P of the cord circuit at the former office is inserted in the jack J of the trunk and the ringing generator is connected therewith, thereby sending current over apath to the-tip strand t of the cord circuit, thence which maybe traced from the generator 2 over the side 3 of the trunk line, the winding 4: of the repeating coil W, conductor 5, to point 6, thence by Way of conductor 7 .to spring 8 of the relay 1* which is connected between the strand 8 of the trunk cord and the live pole of the battery B,

thence by way of conductor 9 to point 10,

thence over conductor 11 and through the winding 12 of relay 1*, conductor 13 to point 14, conductor 15, winding 16 of the repeat ing coil W, sleeve conductor 17 of the trunk circuit, and thence over strand ,9 of the 'cord circuit back to the other side of the generator. The ringing current flowing in this path operates said relay 1' causing it to attractits armatures l8 and 19, thereby closing first the circuit of thetrunk signal S' from the live pole or" the battery B over'conductor 20 to point 21 and thenceby way of."

conductor Z2 through the lamp 5, the for j ward contact of spring 19 and through a suitable pilot relay to ground;

The second circuit is from the conductor- 22 through spring 18 to relay 1 and its forward contact, the locking winding 23 of relay and thence by way of conductor 24 and the normal contact and spring 25 of said relay 1" to ground. Thus the relay 1* is maintained energized and the local circuit of the lamp S closed after the ringing generator in the cord circuit is disconnected. Upon observing this signal S the trunk operator connects her telephone therewith through the medium of thelistening key 26 and obtains the number of the party wanted.

Upon learning the number the wanted line is tested in the usual manner, the test circuit being completed over the tip strand t of the trunk, spring 27 of relay 1 and its normal contact, through the test relay r to ground;

-this test relay controlling a suitable local circuit of the operators set. Upon finding the line idle the plug 1 of the trunk is inserted in the jack of the telephone line and the ringing generator 28 operated. The insertion of the ping I" provides a path for current from the battery B over conductor 29 through the relav r and thence over strand s and through the cutoff relay of the line L to Oground. The cut-off relay is thus operate to place the line in condition for conversation and the relay r is operated and energizes said relay 1' winding 33 of relay W.

" will serves, by attracting its spring 25, to open the circuit to the locking winding of the relay 1" thus permitting the denergization of said relay and the opening of the circuit of the 'nal S, which is accordingly retired. In .ltiou, the attraction of the spring 27 of this relay 9 disconnects the test relay and completes the two portions of the strand 6 of the trunk cord for conversation. At the same time the spring 8 of said relay 1* enits forward ground contactfor a purpose hereinafter described. r

Upon the response of the called subscriber current flows from the battery B overthe sleeve side of the telephone line to the substation to charge the transmitter for talking and thence back to the central oflice over the tip side of the telephone line and through the strand t and conductor 80 to and through relay 1' to other terminal of the battery The relay 7* is therefore era ted, thuslseparating its spring 31 from its back contactand its spring 32 also from its back contact and connecting thesame with its fomvard contact, thereby establishing a circuit rom the live pole of the battery B over conductor 20, through windin 33 of a slow-acting relay 9, conductor 34, orward contact and spring 32 of relay 1", conductor to point 10, thence by way of conductor E spring 8 and its forward contact of relay 7' to ground. The current flowing-in this path during conversation and the relay is made slow acting so that it not quickly let go its springs, all for a purpose to be hereinafter described. One method of accomplishing this retarding effect is to provide the said relay with a copper shell, indicated by dotted lines in the drawing, in which the eddy currents caused by the change in the magnetic field sur-" rounding said relay tend to retard such change and hence its deenergization.

At the end of the conversation, the sub-- pal S which is lighted to apparatus and few parts,

scriber upon the line L hangs up his telephone, thereby deenergizing relay 7 which opens through. its spring 32 the circuit of the Owing to the fact that the relay 1" is made slow acting as above described, the springs 31 and 32 of said rclay 9' reach their normal contacts before the springs 06 and 37 of said relay 1' are separated from their forward contacts. This establishes a circuit from the live pole of the battery l3 over conductor to point 38, spring 36 of relay 7' and its forward contact, the locking Winding 39'of said relay, comluctor 4.0, hack contact and spring 31 of relay 9*", conductor 41 to point 6, conductor 5, winding 4 of repeating coil W, tip side 3 of the trunk line, strand t of the magneto cord circuit, thence through the bridged clearing drop D of the cord circuit, strand sleeve condnctor 17 of the trunk, winding 1.6 of the repeating coil W, conductor 15 to l point 14, conductorz'ifl, spring37 and ion ward contact ofrelay r, wire 13, back contact and-spring 32 of relay 1. branch to point 10, conductor 9, spring 8 of relay 1 to ground. The current in this path maintains the relay 1' energized and also energizes and operates the drop D in the magneto cord circuit to thereby indicate to the magneto operator that the conversation has terminated. In the path just traced the conductors 42, '13 and 35 form a short circuit about winding 1901? rc lay 1' to prevent the same operating. Upon observinggthissignal the operator at (he magneto oflice takes down the cord circuit thereby opening the said path for current from battery B and de'clnergizing relay 7'".

At the same time the relay 7' at the out going end is deenergized and permits current from the battery B which maybe the same as the battery B, to send current over the sleeve side 17 of the trunk, wind mg 16 of repeating coil \V, conduclnr 15 to point 14;, Wire 13, winding 12 of relay 1*, conductor 11 to point 10, conductor 9, spring '8 of relay 7 to ground. The relay 7' being at this time deenergized the windin 152 of the relay 1* is not now short-circu1lnd by conductors 42, 43. and 35. The operation of the relay r closes the local circuit of the siggive the disconnect indication to the incoming operator. As soon as this is obscrved'by the operator she withdraws the plug P which dcencrgizcs the relay 1* and opens the circuit of relay 2* at its spring 8 and forward contact, thus restoring the signal and all other parts to normal condition.

It is thus seen that by extremely simple the desired results are accomplished, and while I have described but one method of doing the work it will be understood that various changes and alterations may be made therein without departing from the scope or principle of the same. The various batteries at each oliicc may obviously be and in practice are one and the same; so too, the various grounds are the common ofiice return or ground connection.

I claim:

1. The combinationwith a trunk circuit extending between a magneto telephone ollice and a. common batter; ollice, of a cord circuit at the former oliice having a bridged clearing-out drop, a subscribers line with which the incoming end of the trunk is adapted to connect, a source of current associated with said end to send current over the line during conversation, and electro magnetic mechanism at the incoming oilicc under the control of the subscriber and including a slow acting relay adapted to be locked in position. to send current back over the outgoing end of the trunk to operate said drop when the subscriber hangs up his ered with the outgoing end of the trunk, substantially as described.

combination wit-ha trunk circuit having a bridged subscriber hangs up current telephone and to be deenergized when connections are severed with the outgoing end of the trunk, substantially as described.

2. The combination with a trunk circuit extending between a magneto telephone oilice and a common battery office, of. a cord circuit at the former otlice having a. bridged clearing-out drop, asubscribers line with' which the incoming end of the trunk is adapted to connect, a source of current associated with said end to send current over the line during conversation, and electro magnetic mechanism at the incoming office under the control of the subscriber and including a slow acting relayadapted to be locked in position to send current from said source back over the outgoing end of the trunk to operate said drop when the subscriber hangs up his telephone and tobe again unlocked when the connection is sev- 3. The combination with a trunk circuit, of a cord circuit to connect with one end and having a lin'idged clearing-out signaling device, a trunk cord at the other end of the trunk to connect the same with a subscribers line, a source of current associated with the cord and line to permit current to the latter for talking, a relay at the incoming end of the trunk controlled by the latter line, a slow acting relay controlled by the first mentioned relay, a locking winding upon said slow acting relay, and circuits suitably controlled by said relays to send from said source through said locking winding over the outgoing end of the trunk to operatesaid bridged signaling device i'nthecord when the subscriber hangs up his telephone, substai itia-lly as described.

4. in a telephone trunking system, the

clearing-out drop and adapted to be connected with the outgoing end of the trunk, a common battery subscribcfls line to be connected with .the other end of the trunk, relay mechanism associated with the incoming end of the trunk and adapted to maintain current over the outgoing end thereof to operate said cord circuit drop after the common battery his telephone and until the conncctionis severed with the outgoing end of the trunk, substantially as described. in a telephone system, the combination with a trunk circuit, of a cord circuit havdevice adapted to connect with circuit of the first circuit, of a cord and adapted to beconnected with the outgoing end of the trunk, a common battery subscribers line to which the other end of the trunk is adapted to connect, a relay associated with the incoming end of the trunk adapted to be actuated by current flowing over the outgoing end of the trunk and through the coil of said bridged supervisory signaling device when the common battery subscriber hangs up his receiver an thereafter until the connection isf severe with the outgoing end of the trunk, substantially as described.

(5. In a telephone system, the combination with a trunk circuit, of a cord circuit having abridged clearing-out drop and adapted to be connected with the outgoing end of the trunk, a common battery subscribers line to which the incoming end of said trunk is the incoming endof said trunk for directing current through the said clearing-out drop when the common battery subscriber hangs up his telephone and thereafter until,the connection is severed with the -ontgoing end of the trunk and for thereafter removing the current source from its connection with said trunk line, substantially as described.

7. In a telephone system, the combination with a trunk circuit, of a cord circuit the outgoing end thereof, and a telephone line with which the incoming-end may be connected, an auxiliary circuit associated with the trunking circuit, a relay tor controlling said auxiliary circuit, a second relay for controlling the circuit of the first relay, the second relay being adapted to close the initial actuating relay when the second relay is in its actuated position, and to close the locking circuit the second relay is in its unactuated position, the circuit of said first relay being interrupted when the armature of the second relay is in an intermediate position, and means for preventing the first relay from becoming sufiiciently deenergized during the movement of the armature of the second relay to open the circuit by its locking coil, substantially as described.

Signed by me at Chicago, county of Cook and State of Illinois in the presence of two witnesses.

CHARLES S. WINSTON. \Vitnesses:

ROBER" LEWIS AMES, lhnrrir F. Gmnn.

of the first relay when adapted to connect, means associated with 

